1. Field of the Invention
The present invention relates generally to an optical filter device, and more particularly to an optical filter device employing electrically switchable holograms.
2. Description of the Relevant Art
Image display systems often employ a display screen for projecting an image. The display screen typically displays a sequence of monochrome images that are illuminated in succession by red, blue, and green light. The illuminated images are then projected for display to a viewer.
The display screen switches from one monochrome image to the next very rapidly so that a sequence of three consecutive monochrome images illuminated by red, blue, and green light, respectively, are projected and effectively eye integrated by a viewer to create a full-color image. The successive illumination of the display screen by red, blue, and green light can be achieved by employing a white-light source and a rotating color wheel (often utilizing transmissive dielectric red, blue, and green filters). These rotating color wheels are prone to mechanical problems. Additionally, rotating wheels tend to be large and noisy in operation.